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Harvard Forest Data Archive

HF004

Canopy-Atmosphere Exchange of Carbon, Water and Energy at Harvard Forest EMS Tower since 1991

Related Publications

Data

Overview

  • Lead: William Munger, Steven Wofsy
  • Investigators: Carol Barford, Shawn Urbanski
  • Contact: J. William Munger
  • Start date: 1991
  • End date: 2017
  • Status: ongoing
  • Location: Prospect Hill Tract (Harvard Forest)
  • Latitude: +42.537755
  • Longitude: -72.171478
  • Elevation: 340 meter
  • Taxa:
  • Release date: 2019
  • Revisions:
  • EML file: knb-lter-hfr.4.30
  • DOI: digital object identifier
  • Related links:
  • Study type: long-term measurement
  • Research topic: forest-atmosphere exchange
  • LTER core area: primary production, inorganic nutrients
  • Keywords: air temperature, carbon, carbon dioxide, eddy covariance, evapotranspiration, heat flux, relative humidity, net ecosystem exchange
  • Abstract:

    The tower-based CO2 measurements and key meteorological drivers are intended to examine how regional and ecosystem level processes in a mid-latitude forest contribute to global carbon cycling. Specifically, we endeavor to understand quantitatively how and why forested ecosystems take up or release carbon, on time scales from hours to decades, and to elucidate responses to climate changes and management interventions.

    The tower was installed 1989 and the resulting eddy-flux measurements constitute the longest running record of the net-ecosystem carbon exchange in a North American Forest. The resulting long-term record of Net Ecosystem Exchange (NEE) has shown the effects of climate anomalies on carbon fluxes for seasonal and annual time scales. For example, reduced soil frost allows greater respiration in the winter leading to lower C sequestration. Cumulative gross photosynthesis depends on when the canopy emerges in the spring. Warmer springtime temperatures lead to greater uptake of C. As the NEE record is extended and augmented by supporting ecological measurements, we can further identify longer-term effects of climate perturbations on carbon fluxes and further define the relationship between stand history and carbon sequestration. Climatic anomalies in one season or year may have a longer-term effect on the sequestration of carbon in subsequent seasons or years.

    The flux and ecological measurements are coordinated with studies at other sites through the AmeriFlux network. By examining the relationships between carbon fluxes and the driving physical and biological variables across a range of sites we are enhancing understanding of the processes that control NEE.

  • Methods:

    Vertical and horizontal wind speeds and sonic temperature are determined using an ATI Sonic Anemometer mounted at 29m. Wind speed and direction and momentum and sensible heat fluxes are computed from the anemometer data. Fast-response CO2-H2O are determined by closed-path IR-Absorbance analyzer. Vertical fluxes are computed on 30-min intervals. Concentration profiles of CO2 are determined by closed-path IR absorbance analyzer sampling from inlets at 30,24,18,12,6, 3,1,0.05m. Calibrated using a pair of absolute standards that bracket the range of ambient concentration. Air temperatures are measured using 30kW thermistors and relative humidity is measured using thin-film capacitor sensors mounted in aspirated radiation shields at 30,22,12,6,3m. Soil temperatures at the litter-soil interface and 20cm 50cm depth are measured with 30kW thermistors. Photosynthetically active photon flux density is determined by Quantum sensors at 29 and 12m. Net radiation is measured using a net radiation sensor.

  • Use:

    This dataset is released to the public under Creative Commons license CC BY (Attribution). Please keep the designated contact person informed of any plans to use the dataset. Consultation or collaboration with the original investigators is strongly encouraged. Publications and data products that make use of the dataset must include proper acknowledgement.

  • Citation:

    Munger W, Wofsy S. 2019. Canopy-Atmosphere Exchange of Carbon, Water and Energy at Harvard Forest EMS Tower since 1991. Harvard Forest Data Archive: HF004.

Detailed Metadata

hf004-01: final data

  1. datetime: date and time for data point
  2. year: year for data point
  3. month: month for data point
  4. seq.from.1990.days: data point time given as sequential day starting at Jan 1, 1990 (EST noon on 1/1/90 = 1.5). Time given at start of hourly intervals. (unit: nominalDay )
  5. doy: day of year (unit: nominalDay )
  6. wind.sp: wind speed measured by sonic anemometer at 29m (unit: metersPerSecond / missing value: NA)
  7. wind.dir: wind direction measured by sonic anemometer at 29m (unit: degree / missing value: NA)
  8. eddy.t: temperature sonic anmemometer speed of sound measuremnet (unit: celsius / missing value: NA)
  9. eddy.q: water vapor concentration at 29 m determined by Licor CO2/H2O sensor (unit: millimolePerMole / missing value: NA)
  10. o3.mlb: inferred concentration from fast response ozone detector (unit: partsPerBillion / missing value: NA)
  11. no.y: total nitrogen oxides concentration (unit: partsPerTrillion / missing value: NA)
  12. s.no.y: standard deviation of NOy concentration in the hour (unit: partsPerTrillion / missing value: NA)
  13. co: CO concentration at 29m (unit: partsPerBillion / missing value: NA)
  14. s.co: standard deviaion of CO concentraition in the hour (unit: partsPerBillion / missing value: NA)
  15. f.co2: observed CO2 eddy covariance fluxes at 29m (unit: micromolePerMeterSquaredPerSecond / missing value: NA)
  16. f.mom: covariance of vertical and horizontal windspeed (unit: number / missing value: NA)
  17. f.heat: sensible heat flux at 29 m (unit: wattPerMeterSquared / missing value: NA)
  18. f.h2o: water vapor eddy covariance flux (unit: millimolePerMeterSquaredPerSecond / missing value: NA)
  19. f.o3: ozone eddy covariance flux (unit: micromolePerMeterSquaredPerHour / missing value: NA)
  20. f.no.y: NOy covariance flux (unit: micromolePerMeterSquaredPerHour / missing value: NA)
  21. r.net: net radiation measured by net radiation sensor at 29m (unit: wattPerMeterSquared / missing value: NA)
  22. par.12.7m: photosynthetically active photon flux at 12.7m, just below main canopy (unit: microeinsteinPerMeterSquaredPerSecond / missing value: NA)
  23. par.29m: photosynthetically active photon flux at 29m, which is above the canopy (unit: microeinsteinPerMeterSquaredPerSecond / missing value: NA)
  24. rh.27.9m: relative humidity at top level 27.9 m (measured in aspirated shield) (unit: dimensionless / missing value: NA)
  25. rh.22.6m: relative humidity at second level 22.6 m (unit: dimensionless / missing value: NA)
  26. rh.15.4m: Relative humidity at third level 15.4 m (unit: dimensionless / missing value: NA)
  27. rh.7.6m: relative humidity at fourth level 7.6 m (unit: dimensionless / missing value: NA)
  28. rh.2.5m: relative humidity at ground level 2.5m (unit: dimensionless / missing value: NA)
  29. ta.27.9m: ambient air temperatures at 27.9m (measured in aspirated shield by precision thermistor) (unit: celsius / missing value: NA)
  30. ta.22.6m: ambient air temperature at 22.6m (unit: celsius / missing value: NA)
  31. ta.15.4m: ambient air temperature at 15.4m (unit: celsius / missing value: NA)
  32. ta.7.6m: ambient air temperature at 7.6m (unit: celsius / missing value: NA)
  33. ta.2.5m: ambient air temperature above ground at 2.5m (unit: celsius / missing value: NA)
  34. ts.srfm: mean temperature at the soil surface (litter-soil interface) average of multiple measurement points (unit: celsius / missing value: NA)
  35. ts.50m: soil temperature at 50cm (single point) (unit: celsius / missing value: NA)
  36. ts.20m: soil temperature at 20cm (unit: celsius / missing value: NA)
  37. co2: ambient CO2 concentration from continuous fast-response analyzer 29m (unit: partsPerMillion / missing value: NA)
  38. co2.stg: CO2 storage term d/dt (integrated column concentration 0-29m) (unit: micromolePerMeterSquaredPerSecond / missing value: NA)
  39. p.amb: ambient atmospheric pressure (unit: pascal / missing value: NA)
  40. ts.srf.adj: adjusted soil surface accounting for changing sensor response beneath accumulating litter. Not computed after 2000 - sensor position adjusted for annual litter accumulation. (unit: celsius / missing value: NA)
  41. par.tot.ue.ms.2: total PAR at 29 meters (unit: microeinsteinPerMeterSquaredPerSecond / missing value: NA)
  42. par.dfs.ue.ms.2: diffuse component of PAR at 29 meters (unit: microeinsteinPerMeterSquaredPerSecond / missing value: NA)

hf004-02: filled data

  1. datetime: date and time
  2. year: year
  3. month: month
  4. doy: day of year; January 1 = 1 (unit: nominalDay )
  5. hour: hour of day in EST; (EST=GMT-5) (unit: nominalHour )
  6. seq.day.90: sequential day starting in 1990, 1 = Jan. 1 1990 (unit: nominalDay )
  7. seq.time.90: sequential time in fractional days; 1.5 is 12 noon January 1 1990 (unit: nominalDay )
  8. obs.nee: observerd NEE (FCO2 + storage) in micromoles CO2/m2/s (unit: micromolePerMeterSquaredPerSecond / missing value: NA)
  9. obs.fco2: observed FCO2 (CO2 eddy covariance flux) in micromoleCO2/m2/s (unit: micromolePerMeterSquaredPerSecond / missing value: NA)
  10. fco2.corr: observed FCO2 + storage correction (unit: micromolePerMeterSquaredPerSecond / missing value: NA)
  11. ustar: observed u* (u* = sqrt(-1 * <u'w'>) in cm/s (unit: centimetersPerSecond / missing value: NA)
  12. nee: net ecosystem exchange filled by model in micromole CO2 /m2/s (unit: micromolePerMeterSquaredPerSecond / missing value: NA)
  13. resp.e: ecosystem respiration filled and derived (see below) e-6mol/m2/s (unit: micromolePerMeterSquaredPerSecond / missing value: NA)
  14. gee: gross ecosystem exchange derived and filled (unit: micromolePerMeterSquaredPerSecond / missing value: NA)
  15. c.flag1: 1 when NEE is filled (nee.obs is NA)
    • 1: NEE is filled
  16. c.flag2: 1 when estimated NEE = observed FCO2 + ‘storage adjustment’
    • 1: estimated NEE = observed FCO2 + ‘storage adjustment’
  17. obs.ta.27m: observed air temperature at 27 m (top of tower) (unit: celsius / missing value: NA)
  18. ta.27m.filled: filled air temperature with missing points replaced by available data (unit: celsius / missing value: NA)
  19. ta1.flag1: 1when Tair interpolated from adjacent profile heights
    • 1: Tair interpolated from adjacent profile heights
  20. ta1.flag2: 1when Tair filled from sonic temperature
    • 1: Tair filled from sonic temperature
  21. ta1.flag3: 1when Tair filled from Fisher Meterological Station data
    • 1: Tair filled from Fisher Meterological Station data
  22. ta1.flag4: 1when Tair from daily mean at Shaler Met Station and mean 24-hour cycle
    • 1: Tair from daily mean at Shaler Met Station and mean 24-hour cycle
  23. ta.2.5m: observed air temperature at 2.5m above ground (unit: celsius / missing value: NA)
  24. ta.2.5m.filled: filled air temperature at 2.5 m above ground (unit: celsius / missing value: NA)
  25. ta5.flag1: 1when Tair interpolated from adjacent profile heights
    • 1: Tair interpolated from adjacent profile heights
  26. ta5.flag2: 1when Tair filled from sonic temperature
    • 1: Tair filled from sonic temperature
  27. ta5.flag3: 1when Tair filled from Fisher Meterological Station data
    • 1: Tair filled from Fisher Meterological Station data
  28. ta5.flag4: 1when Tair from daily mean at Shaler Met Station and mean 24-hour cycle
    • 1: Tair from daily mean at Shaler Met Station and mean 24-hour cycle
  29. par.28m: observed photosynthetically active radiation (PPFD) at 28m (above the canopy) (unit: micromolePerMeterSquaredPerSecond / missing value: NA)
  30. par.28m.filled: filled photosynthetically active radiation (PPFD) (unit: micromolePerMeterSquaredPerSecond / missing value: NA)
  31. p.flag1: 1when missing nighttime points set to 0
    • 1: missing nighttime points set to 0
  32. p.flag2: 1when filled from SUNY-ASRC data
    • 1: filled from SUNY-ASRC data
  33. p.flag3: 1when estimated from global radiation at Fisher Met Station
    • 1: estimated from global radiation at Fisher Met Station
  34. p.flag4: 1when filled with hourly mean in a 30 day window
    • 1: filled with hourly mean in a 30 day window
  35. par.tot.ue.ms.2: total PAR at 29 meters (unit: microeinsteinPerMeterSquaredPerSecond / missing value: NA)
  36. par.dfs.ue.ms.2: diffuse component of PAR at 29 meters (unit: microeinsteinPerMeterSquaredPerSecond / missing value: NA)